The average time to spend at the gym is between 1 hour and 1 hour and 30 minutes. This is including actual workout time and rest periods. This is so that you get enough time to provide efficient exercise for the body, and warm up time to lubricate the muscles and joints that are going to be exercised during each session, but also enough time to take a rest between exercises to avoid any possible injuries from excessive progressive overload. Hope this helps.